Pressure sensitive adhesive comprising vinylpyrrolidone

ABSTRACT

A pressure sensitive adhesive comprising a mixture of  
     a radiation-crosslinkable polymer A) composed of at least 40% by weight of C1 to C18 alkyl (meth)acrylates and  
     a polymer B) composed of at least 20% by weight of vinylpyrrolidone and of less than 40% by weight of C1 to C18 alkyl (meth)acrylates  
     or a pressure sensitive adhesive comprising  
     a radiation-crosslinkable polymer C) composed of at least 40% by weight of C1 to C18 alkyl (meth)acrylates and comprising vinylpyrrolidone as comonomer,  
     the fraction of the polymer B) in the mixture being less than 15% by weight, based on the sum of A)+B), and the amount of vinylpyrrolidone in the polymer C) being less than 15% by weight.

[0001] The invention relates to a pressure sensitive adhesive comprisinga mixture of

[0002] a radiation-crosslinkable polymer A) composed of at least 40% byweight of C1 to C18 alkyl (meth)acrylates and

[0003] a polymer B) composed of at least 20% by weight ofvinylpyrrolidone and of less than 40% by weight of C1 to C18 alkyl(meth)acrylates

[0004] or a pressure sensitive adhesive comprising

[0005] a radiation-crosslinkable polymer C) composed of at least 40% byweight of C1 to C18 alkyl (meth)acrylates and comprisingvinylpyrrolidone as comonomer,

[0006] the fraction of the polymer B) in the mixture being less than 15%by weight, based on the sum of A)+B), and the amount of vinylpyrrolidonein the polymer C) being less than 15% by weight.

[0007] The invention further relates to a process for producingself-adhesive articles by means of this adhesive. With pressuresensitive adhesives (PSAs), here is a desire both for good adhesion(sticking) to the substrate and for sufficient internal strength in theadhesive film (cohesion).

[0008] In the case of radiation-crosslinkable PSAs, the cohesion isbrought about after the adhesive has been coated onto a carrier, bymeans of subsequent, photochemically induced crosslinking.

[0009] Adhesion and cohesion are divergent performance properties.Measures which bring about an improvement in the adhesion are generallyaccompanied at the same time by a deterioration in the cohesion, andvice versa.

[0010] U.S. Pat. No. 4,364,972 discloses acrylate copolymers containingmore than 15% vinylpyrrolidone, and their use as pressure sensitiveadhesives. The k value, as a measure of the molecular weight, is greaterthan 100.

[0011] It is an object of the present invention to improve adhesion andcohesion or the adhesion/cohesion tradeoff.

[0012] This improvement is to be achieved, starting from the existingpolyacrylate PSAs, by means of minimal modifications.

[0013] One particular objective is to improve the adhesion to apolarsubstances, such as polyolefins. We have found that this object isachieved by the pressure sensitive adhesives defined at the outset andby a process for producing self-adhesive articles.

[0014] The invention provides two alternatives:

[0015] a pressure sensitive adhesive comprising polymers A) and B) or

[0016] as the alternative, a pressure sensitive adhesive comprisingpolymer C).

[0017] Features common to the two alternatives include in particular thelow vinylpyrrolidone content of less than 15% by weight.

[0018] Alternative 1: Polymer A) and B)

[0019] The polymer A) is composed of at least 40% by weight, preferablyat least 60% by weight, with particular preference at least 80% byweight, of C₁-C₁₈ alkyl (meth)acrylates.

[0020] Mention may be made in particular of C₁-C₈ alkyl (meth)acrylates,e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl(meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0021] The adhesive preferably includes a photoinitiator, so thatpolymer A) can be crosslinked with UV light. The photoinitiator ispreferably attached to the polymer A).

[0022] By irradiation with high-energy light, especially UV light, thephotoinitiator brings about crosslinking of the polymer, preferably bymeans of a chemical grafting reaction of the photoinitiator with aspatially adjacent polymer chain. Crosslinking may take place inparticular by insertion of a carbonyl group of the photoinitiator intoan adjacent C—H bond to form a —C—C—O—H group.

[0023] The adhesive contains preferably from 0.0001 to 1 mol, withparticular preference from 0.0002 to 0.1, with very particularpreference from 0.0003 to 0.01 mol, of the photoinitiator, or of thephotoinitiator-active molecule group attached to the polymer, per 100 gof polymer A).

[0024] The photoinitiator comprises, for example, acetophenone,benzophenone, benzoin ethers, benzil dialkyl ketals or derivativesthereof.

[0025] The photoinitiator is preferably attached to the polyacrylate.

[0026] With particular preference the photoinitiator is one which isincorporated into the polymer chain by means of free-radicalcopolymerization. For this purpose the photoinitiator preferablycontains an acrylic or (meth)acrylic group.

[0027] Suitable copolymerizable photoinitiators are acetophenonederivatives or benzophenone derivatives which contain at least one,preferably one, ethylenically unsaturated group. The ethylenicallyunsaturated group is preferably an acrylic or methacrylic group.

[0028] The ethylenically unsaturated group may be attached directly tothe phenyl ring of the acetophenone or benzophenone derivative. Ingeneral there is a spacer group located between phenyl ring andethylenically unsaturated group.

[0029] The spacer group may contain, for example, up to 100 carbonatoms.

[0030] Suitable acetophenone or benzophenone derivatives are described,for example, in EP-A-346 734, EP-A-377199 (1st claim), DE-A-4 037 079(1st claim), and DE-A-3 844 444 (1st claim) and by this reference arehereby incorporated into the present specification. Preferredacetophenone and benzophenone derivatives are those of the formula

[0031] in which R¹ stands for an organic radical having up to 30 carbonatoms, R² for a hydrogen atom or a methyl group, and R³ for anunsubstituted or substituted phenyl group or a C₁-C₄ alkyl group.

[0032] R¹ stands with particular preference for an alkylene group, inparticular for a C₂-C₈ alkylene group.

[0033] R³ stands with particular preference for a methyl group or aphenyl group.

[0034] Examples of further monomers of which the polymer A) may becomposed are vinyl esters of carboxylic acids containing up to 20 carbonatoms, vinylaromatics having up to 20 carbon atoms, ethylenicallyunsaturated nitriles, vinyl halides, vinyl ethers of alcohols containingfrom 1 to 10 carbon atoms, aliphatic hydrocarbons having from 2 to 8carbon atoms and 1 or 2 double bonds, or mixtures of these monomers.

[0035] Suitable vinyl esters include in particular vinyl propionate and,with particular preference, vinyl acetate.

[0036] Suitable vinylaromatic compounds include, for example,vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene,4-n-decylstyrene, and, preferably, styrene. Examples of nitriles areacrylonitrile and methacrylonitrile.

[0037] The vinyl halides are ethylenically unsaturated compoundssubstituted by chlorine, fluorine or bromine, preferably vinyl chlorideand vinylidene chloride.

[0038] Examples of vinyl ethers include vinyl methyl ether, vinyl ethylether or vinyl isobutyl ether. Preferred vinylethers are those ofalcohols containing from 1 to 4 carbon atoms.

[0039] As hydrocarbons having from 2 to 8 carbon atoms and two olefinicdouble bonds mention may be made of butadiene, isoprene, andchloroprene.

[0040] Further suitable monomers include in particular monomerscontaining carboxylic acid, sulfonic acid or phosphonic acid groups.Carboxylic acid groups are preferred. Examples that may be mentionedinclude acrylic acid, methacrylic acid, itaconic acid, maleic acid, andfumaric acid.

[0041] Further monomers are also, for example, hydroxyl-containingmonomers, especially C₁-C₁₀ hydroxyalkyl (meth)acrylates, and also(meth)acrylamide.

[0042] Furthermore, mention may be made of phenyloxyethyl glycolmono(meth)acrylate, glycidyl acrylate, glycidyl methacrylate, and amino(meth)acrylates such as 2-aminoethyl (meth)acrylate.

[0043] Monomers which in addition to the double bond carry furtherfunctional groups as well, e.g., isocyanate, amino, hydroxyl, amide orglycidyl, may, for example, improve the substrate adhesion.

[0044] The polymer A) preferably has a K value of not more than 80, inparticular from 30 to 80, with particular preference from 40 to 60,measured in tetrahydrofuran (1% strength solution, 21° C).

[0045] The Fikentscher K value is a measure of the molecular weight andviscosity of a polymer.

[0046] The glass transition temperature (Tg) of the polymer A) ispreferably from −60 to +10° C., with particular preference from −55 to0° C., with very particular preference from −55 to −10° C.

[0047] The glass transition temperature of the polymer A) may bedetermined by customary methods such as differential thermoanalysis ordifferential scanning calorimetry (see, for example, ASTM 3418/82,midpoint temperature).

[0048] Polymers A) may be prepared by copolymerizing the monomericcomponents using the customary polymerization initiators and also, whereappropriate, regulators, polymerization being carried out at thecustomary temperatures in bulk, in emulsion, e.g., in water or liquidhydrocarbons, or in solution. Emulsion polymerization produces aqueousdispersions of the polymer A). The polymers are preferably prepared bypolymerization of the monomers in solvents (solution polymerization), inparticular in solvents with a boiling range from 50 to 150° C.,preferably from 60 to 120° C., using the customary amounts ofpolymerization initiators, which are generally from 0.01 to 10% byweight, in particular from 0.1 to 4% by weight, based on the totalweight of the monomers. Suitable solvents include, in particular,alcohols, such as methanol, ethanol, n- and iso-propanol, n- andiso-butanol, preferably isopropanol and/or isobutanol, and alsohydrocarbons such as toluene and, in particular, petroleum spirits witha boiling range from 60 to 120° C. It is also possible to use ketones,such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, andesters, such as ethyl acetate, and also mixtures of solvents of the typementioned, preference being given to mixtures containing isopropanoland/or isobutanol in amounts of from 5 to 95% by weight, in particularfrom 10 to 80% by weight, preferably from 25 to 60% by weight, based onthe solvent mixture used.

[0049] In the case of solution polymerization, examples of suitablepolymerization initiators include azo compounds, ketone peroxides, andalkyl peroxides.

[0050] Following polymerization in solution, the solvents may whereappropriate be separated off under reduced pressure, operating atelevated temperatures in the range, for example, of from 100 to 150° C.The polymers may then be used in the solvent-free state, i.e., as melts.In some cases it is also of advantage to prepare the polymers bypolymerization in bulk, i.e., without the use of a solvent, in whichcase it is possible to operate batchwise or else continuously, e.g., inaccordance with the details in U.S. Pat. No. 4,042,768.

[0051] The polymers A) used in the mixture of the invention arepreferably solvent-free. A residual amount of solvents, e.g., organicsolvents and/or water, of below 5 parts by weight, in particular below 2parts by weight, with particular preference below 1 part by weight, withvery particular preference below 0.5 part by weight or below 0.1 part byweight, of solvent per 100 parts by weight of the sum of polymer A) andpolymer B), can be present, however.

[0052] In addition to the polymer A), the mixture of the inventionincludes a polymer B) which is composed of at least 20% by weight ofvinylpyrrolidone.

[0053] Polymer B) is preferably composed of at least 30% by weight, withvery particular preference at least 50% by weight, of vinylpyrrolidone.By vinylpyrrolidone in this context is meant N-vinylpyrrolidone.

[0054] Examples of suitable further monomers include all of the monomersalready listed above for polymer A). The further monomers preferablycomprise vinyl esters of carboxylic acids containing up to 20 carbonatoms, in particular those of carboxylic acids containing up to 6 carbonatoms. Mention may be made in particular of vinyl propionate and, withvery particular preference, of vinyl acetate.

[0055] The amount of the vinyl esters can be, for example, 0-80% byweight, in particular from 0 to 70% by weight, and with particularpreference from 0 to 50% by weight, based on polymer B).

[0056] In one particular embodiment, a suitable vinyl ester content isfrom 30 to 70% by weight of vinyl esters, especially vinyl acetate.

[0057] The amount of vinylpyrrolidone and vinyl esters, especially vinylacetate, together is in particular at least 60% by weight, preferably atleast 80% by weight, and also in particular at least 90% by weight.

[0058] Other suitable further monomers include, for example,vinylimidazole and the other monomers mentioned under A). Polymer B) mayalso be radiation-crosslinkable. For this purpose polymer B) preferablyincludes the copolymerizable photoinitiators listed under A).

[0059] Polymer B) need not contain any C₁-C₁₈ alkyl (meth)acrylates. TheC₁-C₁₈ alkyl (meth)acrylate content is therefore below 40% by weight, inparticular below 20% by weight, with particular preference below 5% byweight or at 0% by weight.

[0060] Polymers B) are preferably prepared by free-radicalpolymerization, especially in a solvent (solution polymerization).

[0061] Examples of suitable solvents include water, alcohols or otherpolar organic solvents.

[0062] The polymer B) preferably has a K value of not more than 80, inparticular from 10 to 70, with particular preference from 15 to 60,measured in tetrahydrofuran (1% strength solution, 21° C.).

[0063] The Fikentscher K value is a measure of the molecular weight andviscosity of the polymer.

[0064] Where polymer A) is in the form of an aqueous dispersion, polymerB) can simply be added.

[0065] In the preferred case where polymer A) has been obtained bysolution polymerization in an organic solvent, polymer B) can simply beadded to the solution and, if desired, the solvent can be removedsubsequently.

[0066] This procedure results in particularly advantageous mixtures ofthe polymers A) and B).

[0067] The mixture of the polymers A) and B) and also the pressuresensitive adhesive are preferably free of water and solvent or containat most the residual amounts, already indicated above, of less than 5parts by weight, in particular less than 2 parts by weight; less than 1part by weight, less than 0.5 part by weight, or less than 0.1 part byweight, of water and/or solvent per 100 parts by weight of the sum ofA)+B).

[0068] The fraction of polymer B) is less than 15 parts by weight per100 parts by weight of the sum of A)+B).

[0069] With preference, the amount of the polymer B) is from 0.1 to 14parts by weight, with particular preference from 2 to 14 and veryparticular preference from 5 to 14 and in particular from 10 to 14 partsby weight, per 100 parts by weight of the sum of A)+B).

[0070] Alternative 2: Polymer C)

[0071] In this case the pressure sensitive adhesive includes a polymerC) comprising vinylpyrrolidone as comonomer.

[0072] For polymer C) and for the pressure sensitive adhesive comprisingpolymer C), the comments made above in relation to polymer A) and thepressure sensitive adhesive apply, unless indicated otherwise, in theremarks below.

[0073] The vinylpyrrolidone (i.e. N-vinylpyrrolidone) content of polymerC) is less than 15% by weight, based on polymer C). It is preferablyfrom 2 to 14% by weight, with particular preference from 5 to 14% byweight, and with very particular preference from 10 to 14% by weight.

[0074] Polymer C) as well, like polymer A), is otherwise composedpreferably of C₁-C₁₈ alkyl (meth)acrylates; in particular, the amountthereof in the polymer C) is at least 60% by weight and with particularpreference at least 80% by weight.

[0075] As further monomers polymer C) may also contain vinyl esters,especially vinyl acetate.

[0076] Moreover, polymer C) is radiation-crosslinkable.

[0077] For this purpose the pressure sensitive adhesive preferablyincludes a photoinitiator; with particular preference, saidphotoinitiator is attached to the polymer C).

[0078] Regarding the nature and amount of the photoinitiator, thecomments made above in connection with alternative 1 apply.

[0079] Polymer C) may further comprise the monomers specified forpolymer A) as well.

[0080] Polymer C) preferably has a K value of not more than 80, inparticular from 30 to 80, with particular preference from 40 to 60,measured in tetrahydrofuran (1% strength solution, 21° C.).

[0081] The Fikentscher K value is a measure of the molecular weight andviscosity of the polymer.

[0082] The glass transition temperature (Tg) of the Polymer C) ispreferably from −60 to +10° C., with particular preference from −55 to0° C., with very particular preference from −55 to −10° C. (Regardingthe determination of the glass transition temperature, see above.)

[0083] The preparation takes place to correspond to polymer A);preferably, it is effected by solution polymerization and subsequentremoval of the solvent. Polymer C) and also the pressure sensitiveadhesive are preferably free of solvent and water and contain at most aresidual content as indicated above for A).

[0084] In Relation to Both Alternatives

[0085] The PSAs of the invention may consist solely of the mixture ofpolymer A) and B) or, alternatively, solely of polymer C).

[0086] The PSAs may comprise further additives. Where photoinitiatorsare not already attached to polymer A) and/or C), they may be added tothe PSAs at any desired point in time.

[0087] Examples of further additives include fillers, colorants,leveling assistants, and, in particular, tackifiers (tackifying resins).

[0088] Tackifiers are, for example, natural resins, such as rosins andtheir derivatives formed by disproportionation or isomerization,polymerization, dimerization, and/or hydrogenation. They may be in theirsalt form (with monovalent or polyvalent counterions, for example(cations) or, preferably, in their esterified form. Alcohols used forthe esterification may be monohydric or polyhydric. Examples aremethanol, ethanediol, diethylene glycol, triethylene glycol,1,2,3-propanetriol, and pentaerythritol.

[0089] Use is also made, furthermore, of hydrocarbon resins, e.g.,coumarone-indene resins, polyterpene resins, hydrocarbon resins based onunsaturated CH compounds, such as butadiene, pentene, methylbutene,isoprene, piperylene, divinylmethane, pentadiene, cyclopentene,cyclopentadiene, cyclohexadiene, styrene, α-methylstyrene, andvinyltoluene.

[0090] Polyacrylates which have a low molar weight are also increasinglybeing used as tackifiers. These polyacrylates have a weight-averagemolecular weight M_(w) of preferably less than 30,000. The polyacrylatesare composed preferably of at least 60% by weight, in particular atleast 80% by weight, of C₁-C₈ alkyl (meth)acrylates.

[0091] Preferred tackifiers are natural or chemically modified rosins.Rosins are composed predominantly of abietic acid or derivatives ofabietic acid.

[0092] The amount by weight of the tackifiers is, for example, from 5 to100 parts by weight, with particular preference from 10 to 50 parts byweight, per 100 parts by weight of polyacrylate (solids/solids).

[0093] These pressure sensitive adhesives are preferably used as hotmeltPSAs; that is, they are applied from the melt to the desired carriers.

[0094] The PSAs and hotmelt adhesives of the invention are particularlysuitable for producing self-adhesive articles, such as labels, adhesivetapes or adhesive sheets, e.g., protective films.

[0095] The self-adhesive articles are generally composed of a carrier orbacking and a film of the adhesive applied to one or both sides,preferably one side.

[0096] The backing material may comprise, for example, paper or apolymer film made from polyolefins or PVC.

[0097] The self-adhesive articles are produced in particular by applyingthe pressure sensitive adhesive to the backing and subsequentlyeffecting crosslinking with UV light.

[0098] The self-adhesive articles are suitable for a very wide varietyof substrates. The substrates may be of metals, paper, card, wood,plastics, etc.

[0099] It is a particular advantage of the invention that using thepressure sensitive adhesives of the invention very good adhesion isachieved by the self-adhesive articles even on apolar surfaces,particularly on surfaces of polyolefins, e.g., polyethylene orpolypropylene.

[0100] In general, very good adhesion and cohesion are achieved.

EXAMPLES

[0101] Pressure Sensitive Adhesive 1 (PSA1)

[0102] This is a mixture of polyacrylate (polymer A)) with apolyvinylpyrrolidone (polymer B)), prepared by solution polymerizationof the polyacrylate, addition of the polyvinylpyrrolidone, and removalof the solvent by distillation.

[0103] Polymer A) is composed of 94.7% by weight n-butyl acrylate (BA) 5% by weight acrylic acid (AA)  0.3% by weight photoinitiator (P) ofthe above formula I K value 45.8

[0104] Polymer B) was composed exclusively of N-vinylpyrrolidone; Kvalue=17

[0105] The weight ratio of A) to B) was 90:10.

[0106] Pressure Sensitive Adhesive 2 (PSA2)

[0107] Polymer C) was composed of: 84.7% by weight BA 10% by weightvinylpyrrolidone (VP)  5% by weight AA  0.3% by weight P K value was47.3.

[0108] Pressure Sensitive Adhesive 3 (PSA3) (for Comparison)

[0109] Polymer C) was composed of: 77.7% by weight BA 17% by weight VP 5% by weight AA  0.3% by weight P K value was 47.3.

[0110] The pressure sensitive adhesives PSA1-PSA3 are hotmelt adhesiveswhich are water-free and solvent-free.

[0111] Performance Testing

[0112] The pressure sensitive adhesives PSA1-PSA3 were coated with anapplication rate of 60 g/m² onto polyester film (Hostaphan RN 36),placed on a conveyor belt, and irradiated with 10 mJ/cm² (UV-C²radiation).

[0113] This was followed by measurements of the peel strength (adhesion)and shear strength (cohesion).

[0114] The PSA-coated backing was cut into test strips 25 mm wide. Todetermine the shear strength the test strips were bonded with an area of25 mm² to a chromed V2A stainless steel test plate, rolled on once witha 1 kg roller, stored for 10 minutes (under standard conditions, 50%relative humidity, 1 bar, 23° C.), and then loaded in suspended formwith a 1 kg weight (under standard conditions). The measure of the shearstrength was the time taken for the weight to fall off; in each case theaverage from 5 measurements was calculated.

[0115] For determining the peel strength (adhesion) a 2.5 cm wide teststrip was bonded to a chromed V2A stainless steel test plate(alternatively to polypropylene film (PP, see table)) and rolled on oncewith a 1 kg roller. It was then clamped by one end into the upper jaw ofa stress/strain testing apparatus. The adhesive strip was pulled fromthe test area at 300 mm/min at an angle of 180°, i.e., the test stripwas bent over and pulled off parallel to the metal test plate, and theforce required to do this was measured. The measure of the peel strengthwas the force, in N/2.5 cm, which resulted as the average value fromfive measurements.

[0116] The peel strength was determined 24 hours after bonding. Afterthis time, the bond strength has developed fully. TABLE 1 Peel strengthPeel strength N/25 mm N/25 mm Shear strength Adhe- steel 24 h 25 × 25 mmsive 1st min 24 h PP steel PSA1 11.8 20.5 5.8 98h18′ PSA2 11.0 15.9 7.345h31′ PSA3 13.6 17.9 0.5 64h31′

We claim:
 1. A pressure sensitive adhesive comprising a mixture of a radiation-crosslinkable polymer A) composed of at least 40% by weight of C1 to C18 alkyl (meth)acrylates and a polymer B) composed of at least 20% by weight of vinylpyrrolidone and of less than 40% by weight of C1 to C18 alkyl (meth)acrylates or a pressure sensitive adhesive comprising a radiation-crosslinkable polymer C) composed of at least 40% by weight of C1 to C18 alkyl (meth)acrylates and comprising vinylpyrrolidone as comonomer, the fraction of the polymer B) in the mixture being less than 15% by weight, based on the sum of A)+B), and the amount of vinylpyrrolidone in the polymer C) being less than 15% by weight.
 2. An adhesive as claimed in claim 1, wherein the polymers A) and C) are composed of at least 60% by weight of C1 to C18 alkyl (meth)acrylates.
 3. An adhesive as claimed in claim 1, wherein the amount of polymer B) is at least 2% by weight, based on the sum of A)+B), or the polymer C) is composed of at least 2% by weight of vinylpyrrolidone.
 4. An adhesive as claimed in claim 1, wherein the polymers A) and C) are prepared by emulsion polymerization and are present in the form of an aqueous dispersion.
 5. An adhesive as claimed in claim 1, wherein the polymers A) and C) are prepared by solution polymerization in an organic solvent.
 6. An adhesive as claimed in claim 1, wherein the polymers A), B) and C) have a Fikentscher K value of not more than 80 (in 1% strength solution, in tetrahydrofuran solvent, at 21° C.).
 7. An adhesive as claimed in claim 1, comprising a photoinitiator.
 8. An adhesive as claimed in claim 7, wherein the photoinitiator was attached to the polymer A) or the polymer C).
 9. An adhesive as claimed in claim 1, wherein the polymer B) is added to the aqueous dispersion of the polymer A).
 10. An adhesive as claimed in claim 1, wherein the polymer B) is added to the organic solution of polymer A) and then the solvent is separated off.
 11. An adhesive as claimed in claim 1, wherein the amount of water and organic solvents is less than 5 parts by weight per 100 parts by weight of the sum of A) and B) or per 100 parts by weight of C).
 12. An adhesive as claimed in claim 1, which is a hotmelt adhesive.
 13. The use of the adhesive of claim 1, for producing self-adhesive articles, especially labels and adhesive tapes.
 14. A process for producing self-adhesive articles, which comprises drying an adhesive as claimed in claim 1 to substrates, e.g., labels, adhesive tapes or films, and subsequently effecting crosslinking by UV light.
 15. A self-adhesive article obtainable by a process as claimed in claim
 14. 16. A self-adhesive article coated with an adhesive as claimed in claim
 1. 